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revision 1.61, Tue Feb 7 20:54:24 2006 UTC revision 1.97, Thu Jul 18 18:21:22 2013 UTC
# Line 1  Line 1 
1  /*  /*
2   * %W% %E%   * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
3     * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4   *   *
5   * Copyright 2006 Sun Microsystems, Inc. All rights reserved.   * This code is free software; you can redistribute it and/or modify it
6   * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.   * under the terms of the GNU General Public License version 2 only, as
7     * published by the Free Software Foundation.  Oracle designates this
8     * particular file as subject to the "Classpath" exception as provided
9     * by Oracle in the LICENSE file that accompanied this code.
10     *
11     * This code is distributed in the hope that it will be useful, but WITHOUT
12     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13     * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14     * version 2 for more details (a copy is included in the LICENSE file that
15     * accompanied this code).
16     *
17     * You should have received a copy of the GNU General Public License version
18     * 2 along with this work; if not, write to the Free Software Foundation,
19     * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20     *
21     * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22     * or visit www.oracle.com if you need additional information or have any
23     * questions.
24   */   */
25    
26  package java.util;  package java.util;
27    import java.util.function.Consumer;
28    import java.util.stream.Stream;
29    
30  /**  /**
31   * An unbounded priority {@linkplain Queue queue} based on a priority   * An unbounded priority {@linkplain Queue queue} based on a priority heap.
32   * heap.  The elements of the priority queue are ordered according to   * The elements of the priority queue are ordered according to their
33   * their {@linkplain Comparable natural ordering}, or by a {@link   * {@linkplain Comparable natural ordering}, or by a {@link Comparator}
34   * Comparator} provided at queue construction time, depending on which   * provided at queue construction time, depending on which constructor is
35   * constructor is used.  A priority queue does not permit   * used.  A priority queue does not permit {@code null} elements.
36   * <tt>null</tt> elements.  A priority queue relying on natural   * A priority queue relying on natural ordering also does not permit
37   * ordering also does not permit insertion of non-comparable objects   * insertion of non-comparable objects (doing so may result in
38   * (doing so may result in <tt>ClassCastException</tt>).   * {@code ClassCastException}).
39   *   *
40   * <p>The <em>head</em> of this queue is the <em>least</em> element   * <p>The <em>head</em> of this queue is the <em>least</em> element
41   * with respect to the specified ordering.  If multiple elements are   * with respect to the specified ordering.  If multiple elements are
42   * tied for least value, the head is one of those elements -- ties are   * tied for least value, the head is one of those elements -- ties are
43   * broken arbitrarily.  The queue retrieval operations <tt>poll</tt>,   * broken arbitrarily.  The queue retrieval operations {@code poll},
44   * <tt>remove</tt>, <tt>peek</tt>, and <tt>element</tt> access the   * {@code remove}, {@code peek}, and {@code element} access the
45   * element at the head of the queue.   * element at the head of the queue.
46   *   *
47   * <p>A priority queue is unbounded, but has an internal   * <p>A priority queue is unbounded, but has an internal
# Line 36  Line 56 
56   * Iterator} interfaces.  The Iterator provided in method {@link   * Iterator} interfaces.  The Iterator provided in method {@link
57   * #iterator()} is <em>not</em> guaranteed to traverse the elements of   * #iterator()} is <em>not</em> guaranteed to traverse the elements of
58   * the priority queue in any particular order. If you need ordered   * the priority queue in any particular order. If you need ordered
59   * traversal, consider using <tt>Arrays.sort(pq.toArray())</tt>.   * traversal, consider using {@code Arrays.sort(pq.toArray())}.
60   *   *
61   * <p> <strong>Note that this implementation is not synchronized.</strong>   * <p> <strong>Note that this implementation is not synchronized.</strong>
62   * Multiple threads should not access a <tt>PriorityQueue</tt>   * Multiple threads should not access a {@code PriorityQueue}
63   * instance concurrently if any of the threads modifies the list   * instance concurrently if any of the threads modifies the queue.
64   * structurally. Instead, use the thread-safe {@link   * Instead, use the thread-safe {@link
65   * java.util.concurrent.PriorityBlockingQueue} class.   * java.util.concurrent.PriorityBlockingQueue} class.
66   *   *
67   * <p>Implementation note: this implementation provides O(log(n)) time   * <p>Implementation note: this implementation provides
68   * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,   * O(log(n)) time for the enqueing and dequeing methods
69   * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the   * ({@code offer}, {@code poll}, {@code remove()} and {@code add});
70   * <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and   * linear time for the {@code remove(Object)} and {@code contains(Object)}
71   * constant time for the retrieval methods (<tt>peek</tt>,   * methods; and constant time for the retrieval methods
72   * <tt>element</tt>, and <tt>size</tt>).   * ({@code peek}, {@code element}, and {@code size}).
73   *   *
74   * <p>This class is a member of the   * <p>This class is a member of the
75   * <a href="{@docRoot}/../guide/collections/index.html">   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
76   * Java Collections Framework</a>.   * Java Collections Framework</a>.
77     *
78   * @since 1.5   * @since 1.5
79   * @version 1.8, 08/27/05   * @author Josh Bloch, Doug Lea
  * @author Josh Bloch  
80   * @param <E> the type of elements held in this collection   * @param <E> the type of elements held in this collection
81   */   */
82  public class PriorityQueue<E> extends AbstractQueue<E>  public class PriorityQueue<E> extends AbstractQueue<E>
# Line 74  Line 94 
94       * heap and each descendant d of n, n <= d.  The element with the       * heap and each descendant d of n, n <= d.  The element with the
95       * lowest value is in queue[0], assuming the queue is nonempty.       * lowest value is in queue[0], assuming the queue is nonempty.
96       */       */
97      private transient Object[] queue;      transient Object[] queue; // non-private to simplify nested class access
98    
99      /**      /**
100       * The number of elements in the priority queue.       * The number of elements in the priority queue.
# Line 91  Line 111 
111       * The number of times this priority queue has been       * The number of times this priority queue has been
112       * <i>structurally modified</i>.  See AbstractList for gory details.       * <i>structurally modified</i>.  See AbstractList for gory details.
113       */       */
114      private transient int modCount = 0;      transient int modCount = 0; // non-private to simplify nested class access
115    
116      /**      /**
117       * Creates a <tt>PriorityQueue</tt> with the default initial       * Creates a {@code PriorityQueue} with the default initial
118       * capacity (11) that orders its elements according to their       * capacity (11) that orders its elements according to their
119       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
120       */       */
# Line 103  Line 123 
123      }      }
124    
125      /**      /**
126       * Creates a <tt>PriorityQueue</tt> with the specified initial       * Creates a {@code PriorityQueue} with the specified initial
127       * capacity that orders its elements according to their       * capacity that orders its elements according to their
128       * {@linkplain Comparable natural ordering}.       * {@linkplain Comparable natural ordering}.
129       *       *
130       * @param initialCapacity the initial capacity for this priority queue       * @param initialCapacity the initial capacity for this priority queue
131       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less       * @throws IllegalArgumentException if {@code initialCapacity} is less
132       * than 1       * than 1
133       */       */
134      public PriorityQueue(int initialCapacity) {      public PriorityQueue(int initialCapacity) {
# Line 116  Line 136 
136      }      }
137    
138      /**      /**
139       * Creates a <tt>PriorityQueue</tt> with the specified initial capacity       * Creates a {@code PriorityQueue} with the specified initial capacity
140       * that orders its elements according to the specified comparator.       * that orders its elements according to the specified comparator.
141       *       *
142       * @param  initialCapacity the initial capacity for this priority queue       * @param  initialCapacity the initial capacity for this priority queue
143       * @param  comparator the comparator that will be used to order       * @param  comparator the comparator that will be used to order this
144       *         this priority queue.  If <tt>null</tt>, the <i>natural       *         priority queue.  If {@code null}, the {@linkplain Comparable
145       *         ordering</i> of the elements will be used.       *         natural ordering} of the elements will be used.
146       * @throws IllegalArgumentException if <tt>initialCapacity</tt> is       * @throws IllegalArgumentException if {@code initialCapacity} is
147       *         less than 1       *         less than 1
148       */       */
149      public PriorityQueue(int initialCapacity,      public PriorityQueue(int initialCapacity,
# Line 137  Line 157 
157      }      }
158    
159      /**      /**
160       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
161       * specified collection.   If the specified collection is an       * specified collection.  If the specified collection is an instance of
162       * instance of a {@link java.util.SortedSet} or is another       * a {@link SortedSet} or is another {@code PriorityQueue}, this
163       * <tt>PriorityQueue</tt>, the priority queue will be ordered       * priority queue will be ordered according to the same ordering.
164       * according to the same ordering.  Otherwise, this priority queue       * Otherwise, this priority queue will be ordered according to the
165       * will be ordered according to the natural ordering of its elements.       * {@linkplain Comparable natural ordering} of its elements.
166       *       *
167       * @param  c the collection whose elements are to be placed       * @param  c the collection whose elements are to be placed
168       *         into this priority queue       *         into this priority queue
# Line 152  Line 172 
172       * @throws NullPointerException if the specified collection or any       * @throws NullPointerException if the specified collection or any
173       *         of its elements are null       *         of its elements are null
174       */       */
175        @SuppressWarnings("unchecked")
176      public PriorityQueue(Collection<? extends E> c) {      public PriorityQueue(Collection<? extends E> c) {
177          initFromCollection(c);          if (c instanceof SortedSet<?>) {
178          if (c instanceof SortedSet)              SortedSet<? extends E> ss = (SortedSet<? extends E>) c;
179              comparator = (Comparator<? super E>)              this.comparator = (Comparator<? super E>) ss.comparator();
180                  ((SortedSet<? extends E>)c).comparator();              initElementsFromCollection(ss);
181          else if (c instanceof PriorityQueue)          }
182              comparator = (Comparator<? super E>)          else if (c instanceof PriorityQueue<?>) {
183                  ((PriorityQueue<? extends E>)c).comparator();              PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;
184                this.comparator = (Comparator<? super E>) pq.comparator();
185                initFromPriorityQueue(pq);
186            }
187          else {          else {
188              comparator = null;              this.comparator = null;
189              heapify();              initFromCollection(c);
190          }          }
191      }      }
192    
193      /**      /**
194       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
195       * specified priority queue.  This priority queue will be       * specified priority queue.  This priority queue will be
196       * ordered according to the same ordering as the given priority       * ordered according to the same ordering as the given priority
197       * queue.       * queue.
198       *       *
199       * @param  c the priority queue whose elements are to be placed       * @param  c the priority queue whose elements are to be placed
200       *         into this priority queue       *         into this priority queue
201       * @throws ClassCastException if elements of <tt>c</tt> cannot be       * @throws ClassCastException if elements of {@code c} cannot be
202       *         compared to one another according to <tt>c</tt>'s       *         compared to one another according to {@code c}'s
203       *         ordering       *         ordering
204       * @throws NullPointerException if the specified priority queue or any       * @throws NullPointerException if the specified priority queue or any
205       *         of its elements are null       *         of its elements are null
206       */       */
207        @SuppressWarnings("unchecked")
208      public PriorityQueue(PriorityQueue<? extends E> c) {      public PriorityQueue(PriorityQueue<? extends E> c) {
209          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
210          initFromCollection(c);          initFromPriorityQueue(c);
211      }      }
212    
213      /**      /**
214       * Creates a <tt>PriorityQueue</tt> containing the elements in the       * Creates a {@code PriorityQueue} containing the elements in the
215       * specified sorted set.  This priority queue will be ordered       * specified sorted set.  This priority queue will be ordered
216       * according to the same ordering as the given sorted set.       * according to the same ordering as the given sorted set.
217       *       *
218       * @param  c the sorted set whose elements are to be placed       * @param  c the sorted set whose elements are to be placed
219       *         into this priority queue.       *         into this priority queue
220       * @throws ClassCastException if elements of the specified sorted       * @throws ClassCastException if elements of the specified sorted
221       *         set cannot be compared to one another according to the       *         set cannot be compared to one another according to the
222       *         sorted set's ordering       *         sorted set's ordering
223       * @throws NullPointerException if the specified sorted set or any       * @throws NullPointerException if the specified sorted set or any
224       *         of its elements are null       *         of its elements are null
225       */       */
226        @SuppressWarnings("unchecked")
227      public PriorityQueue(SortedSet<? extends E> c) {      public PriorityQueue(SortedSet<? extends E> c) {
228          comparator = (Comparator<? super E>)c.comparator();          this.comparator = (Comparator<? super E>) c.comparator();
229            initElementsFromCollection(c);
230        }
231    
232        private void initFromPriorityQueue(PriorityQueue<? extends E> c) {
233            if (c.getClass() == PriorityQueue.class) {
234                this.queue = c.toArray();
235                this.size = c.size();
236            } else {
237          initFromCollection(c);          initFromCollection(c);
238      }      }
239        }
240    
241      /**      private void initElementsFromCollection(Collection<? extends E> c) {
      * Initialize queue array with elements from the given Collection.  
      * @param c the collection  
      */  
     private void initFromCollection(Collection<? extends E> c) {  
242          Object[] a = c.toArray();          Object[] a = c.toArray();
243          // If c.toArray incorrectly doesn't return Object[], copy it.          // If c.toArray incorrectly doesn't return Object[], copy it.
244          if (a.getClass() != Object[].class)          if (a.getClass() != Object[].class)
245              a = Arrays.copyOf(a, a.length, Object[].class);              a = Arrays.copyOf(a, a.length, Object[].class);
246          queue = a;          int len = a.length;
247          size = a.length;          if (len == 1 || this.comparator != null)
248                for (int i = 0; i < len; i++)
249                    if (a[i] == null)
250                        throw new NullPointerException();
251            this.queue = a;
252            this.size = a.length;
253      }      }
254    
255      /**      /**
256         * Initializes queue array with elements from the given Collection.
257         *
258         * @param c the collection
259         */
260        private void initFromCollection(Collection<? extends E> c) {
261            initElementsFromCollection(c);
262            heapify();
263        }
264    
265        /**
266         * The maximum size of array to allocate.
267         * Some VMs reserve some header words in an array.
268         * Attempts to allocate larger arrays may result in
269         * OutOfMemoryError: Requested array size exceeds VM limit
270         */
271        private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
272    
273        /**
274       * Increases the capacity of the array.       * Increases the capacity of the array.
275       *       *
276       * @param minCapacity the desired minimum capacity       * @param minCapacity the desired minimum capacity
277       */       */
278      private void grow(int minCapacity) {      private void grow(int minCapacity) {
         if (minCapacity < 0) // overflow  
             throw new OutOfMemoryError();  
279          int oldCapacity = queue.length;          int oldCapacity = queue.length;
280          // Double size if small; else grow by 50%          // Double size if small; else grow by 50%
281          int newCapacity = ((oldCapacity < 64)?          int newCapacity = oldCapacity + ((oldCapacity < 64) ?
282                             ((oldCapacity + 1) * 2):                                           (oldCapacity + 2) :
283                             ((oldCapacity / 2) * 3));                                           (oldCapacity >> 1));
284          if (newCapacity < 0) // overflow          // overflow-conscious code
285              newCapacity = Integer.MAX_VALUE;          if (newCapacity - MAX_ARRAY_SIZE > 0)
286          if (newCapacity < minCapacity)              newCapacity = hugeCapacity(minCapacity);
             newCapacity = minCapacity;  
287          queue = Arrays.copyOf(queue, newCapacity);          queue = Arrays.copyOf(queue, newCapacity);
288      }      }
289    
290        private static int hugeCapacity(int minCapacity) {
291            if (minCapacity < 0) // overflow
292                throw new OutOfMemoryError();
293            return (minCapacity > MAX_ARRAY_SIZE) ?
294                Integer.MAX_VALUE :
295                MAX_ARRAY_SIZE;
296        }
297    
298      /**      /**
299       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
300       *       *
301       * @return <tt>true</tt> (as specified by {@link Collection#add})       * @return {@code true} (as specified by {@link Collection#add})
302       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
303       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
304       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 252  Line 311 
311      /**      /**
312       * Inserts the specified element into this priority queue.       * Inserts the specified element into this priority queue.
313       *       *
314       * @return <tt>true</tt> (as specified by {@link Queue#offer})       * @return {@code true} (as specified by {@link Queue#offer})
315       * @throws ClassCastException if the specified element cannot be       * @throws ClassCastException if the specified element cannot be
316       *         compared with elements currently in this priority queue       *         compared with elements currently in this priority queue
317       *         according to the priority queue's ordering       *         according to the priority queue's ordering
# Line 273  Line 332 
332          return true;          return true;
333      }      }
334    
335        @SuppressWarnings("unchecked")
336      public E peek() {      public E peek() {
337          if (size == 0)          return (size == 0) ? null : (E) queue[0];
             return null;  
         return (E) queue[0];  
338      }      }
339    
340      private int indexOf(Object o) {      private int indexOf(Object o) {
# Line 290  Line 348 
348    
349      /**      /**
350       * Removes a single instance of the specified element from this queue,       * Removes a single instance of the specified element from this queue,
351       * if it is present.  More formally, removes an element <tt>e</tt> such       * if it is present.  More formally, removes an element {@code e} such
352       * that <tt>o.equals(e)</tt>, if this queue contains one or more such       * that {@code o.equals(e)}, if this queue contains one or more such
353       * elements.  Returns true if this queue contained the specified element       * elements.  Returns {@code true} if and only if this queue contained
354       * (or equivalently, if this queue changed as a result of the call).       * the specified element (or equivalently, if this queue changed as a
355         * result of the call).
356       *       *
357       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
358       * @return <tt>true</tt> if this queue changed as a result of the call       * @return {@code true} if this queue changed as a result of the call
359       */       */
360      public boolean remove(Object o) {      public boolean remove(Object o) {
361          int i = indexOf(o);          int i = indexOf(o);
# Line 313  Line 372 
372       * Needed by iterator.remove.       * Needed by iterator.remove.
373       *       *
374       * @param o element to be removed from this queue, if present       * @param o element to be removed from this queue, if present
375       * @return <tt>true</tt> if removed       * @return {@code true} if removed
376       */       */
377      boolean removeEq(Object o) {      boolean removeEq(Object o) {
378          for (int i = 0; i < size; i++) {          for (int i = 0; i < size; i++) {
# Line 326  Line 385 
385      }      }
386    
387      /**      /**
388       * Returns <tt>true</tt> if this queue contains the specified element.       * Returns {@code true} if this queue contains the specified element.
389       * More formally, returns <tt>true</tt> if and only if this queue contains       * More formally, returns {@code true} if and only if this queue contains
390       * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.       * at least one element {@code e} such that {@code o.equals(e)}.
391       *       *
392       * @param o object to be checked for containment in this queue       * @param o object to be checked for containment in this queue
393       * @return <tt>true</tt> if this queue contains the specified element       * @return {@code true} if this queue contains the specified element
394       */       */
395      public boolean contains(Object o) {      public boolean contains(Object o) {
396          return indexOf(o) != -1;          return indexOf(o) != -1;
397      }      }
398    
399      /**      /**
400       * Returns an array containing all of the elements in this queue,       * Returns an array containing all of the elements in this queue.
401       * The elements are in no particular order.       * The elements are in no particular order.
402       *       *
403       * <p>The returned array will be "safe" in that no references to it are       * <p>The returned array will be "safe" in that no references to it are
404       * maintained by this list.  (In other words, this method must allocate       * maintained by this queue.  (In other words, this method must allocate
405       * a new array).  The caller is thus free to modify the returned array.       * a new array).  The caller is thus free to modify the returned array.
406       *       *
407         * <p>This method acts as bridge between array-based and collection-based
408         * APIs.
409         *
410       * @return an array containing all of the elements in this queue       * @return an array containing all of the elements in this queue
411       */       */
412      public Object[] toArray() {      public Object[] toArray() {
# Line 352  Line 414 
414      }      }
415    
416      /**      /**
417       * Returns an array containing all of the elements in this queue.       * Returns an array containing all of the elements in this queue; the
418       * The elements are in no particular order.  The runtime type of       * runtime type of the returned array is that of the specified array.
419       * the returned array is that of the specified array.  If the queue       * The returned array elements are in no particular order.
420       * fits in the specified array, it is returned therein.       * If the queue fits in the specified array, it is returned therein.
421       * Otherwise, a new array is allocated with the runtime type of       * Otherwise, a new array is allocated with the runtime type of the
422       * the specified array and the size of this queue.       * specified array and the size of this queue.
423       *       *
424       * <p>If the queue fits in the specified array with room to spare       * <p>If the queue fits in the specified array with room to spare
425       * (i.e., the array has more elements than the queue), the element in       * (i.e., the array has more elements than the queue), the element in
426       * the array immediately following the end of the collection is set to       * the array immediately following the end of the collection is set to
427       * <tt>null</tt>.  (This is useful in determining the length of the       * {@code null}.
428       * queue <i>only</i> if the caller knows that the queue does not contain       *
429       * any null elements.)       * <p>Like the {@link #toArray()} method, this method acts as bridge between
430         * array-based and collection-based APIs.  Further, this method allows
431         * precise control over the runtime type of the output array, and may,
432         * under certain circumstances, be used to save allocation costs.
433         *
434         * <p>Suppose {@code x} is a queue known to contain only strings.
435         * The following code can be used to dump the queue into a newly
436         * allocated array of {@code String}:
437         *
438         *  <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
439         *
440         * Note that {@code toArray(new Object[0])} is identical in function to
441         * {@code toArray()}.
442       *       *
443       * @param a the array into which the elements of the queue are to       * @param a the array into which the elements of the queue are to
444       *          be stored, if it is big enough; otherwise, a new array of the       *          be stored, if it is big enough; otherwise, a new array of the
445       *          same runtime type is allocated for this purpose.       *          same runtime type is allocated for this purpose.
446       * @return an array containing the elements of the queue       * @return an array containing all of the elements in this queue
447       * @throws ArrayStoreException if the runtime type of the specified array       * @throws ArrayStoreException if the runtime type of the specified array
448       *         is not a supertype of the runtime type of every element in       *         is not a supertype of the runtime type of every element in
449       *         this queue       *         this queue
450       * @throws NullPointerException if the specified array is null       * @throws NullPointerException if the specified array is null
451       */       */
452        @SuppressWarnings("unchecked")
453      public <T> T[] toArray(T[] a) {      public <T> T[] toArray(T[] a) {
454            final int size = this.size;
455          if (a.length < size)          if (a.length < size)
456              // Make a new array of a's runtime type, but my contents:              // Make a new array of a's runtime type, but my contents:
457              return (T[]) Arrays.copyOf(queue, size, a.getClass());              return (T[]) Arrays.copyOf(queue, size, a.getClass());
# Line 418  Line 494 
494           * after we've completed the "normal" iteration.           * after we've completed the "normal" iteration.
495           *           *
496           * We expect that most iterations, even those involving removals,           * We expect that most iterations, even those involving removals,
497           * will not use need to store elements in this field.           * will not need to store elements in this field.
498           */           */
499          private ArrayDeque<E> forgetMeNot = null;          private ArrayDeque<E> forgetMeNot = null;
500    
# Line 430  Line 506 
506    
507          /**          /**
508           * The modCount value that the iterator believes that the backing           * The modCount value that the iterator believes that the backing
509           * List should have.  If this expectation is violated, the iterator           * Queue should have.  If this expectation is violated, the iterator
510           * has detected concurrent modification.           * has detected concurrent modification.
511           */           */
512          private int expectedModCount = modCount;          private int expectedModCount = modCount;
# Line 440  Line 516 
516                  (forgetMeNot != null && !forgetMeNot.isEmpty());                  (forgetMeNot != null && !forgetMeNot.isEmpty());
517          }          }
518    
519            @SuppressWarnings("unchecked")
520          public E next() {          public E next() {
521              if (expectedModCount != modCount)              if (expectedModCount != modCount)
522                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
# Line 457  Line 534 
534          public void remove() {          public void remove() {
535              if (expectedModCount != modCount)              if (expectedModCount != modCount)
536                  throw new ConcurrentModificationException();                  throw new ConcurrentModificationException();
             if (lastRet == -1 && lastRetElt == null)  
                 throw new IllegalStateException();  
537              if (lastRet != -1) {              if (lastRet != -1) {
538                  E moved = PriorityQueue.this.removeAt(lastRet);                  E moved = PriorityQueue.this.removeAt(lastRet);
539                  lastRet = -1;                  lastRet = -1;
# Line 466  Line 541 
541                      cursor--;                      cursor--;
542                  else {                  else {
543                      if (forgetMeNot == null)                      if (forgetMeNot == null)
544                          forgetMeNot = new ArrayDeque<E>();                          forgetMeNot = new ArrayDeque<>();
545                      forgetMeNot.add(moved);                      forgetMeNot.add(moved);
546                  }                  }
547              } else {              } else if (lastRetElt != null) {
548                  PriorityQueue.this.removeEq(lastRetElt);                  PriorityQueue.this.removeEq(lastRetElt);
549                  lastRetElt = null;                  lastRetElt = null;
550                } else {
551                    throw new IllegalStateException();
552              }              }
553              expectedModCount = modCount;              expectedModCount = modCount;
554          }          }
   
555      }      }
556    
557      public int size() {      public int size() {
# Line 493  Line 569 
569          size = 0;          size = 0;
570      }      }
571    
572        @SuppressWarnings("unchecked")
573      public E poll() {      public E poll() {
574          if (size == 0)          if (size == 0)
575              return null;              return null;
# Line 516  Line 593 
593       * i.  Under these circumstances, this method returns the element       * i.  Under these circumstances, this method returns the element
594       * that was previously at the end of the list and is now at some       * that was previously at the end of the list and is now at some
595       * position before i. This fact is used by iterator.remove so as to       * position before i. This fact is used by iterator.remove so as to
596       * avoid missing traverseing elements.       * avoid missing traversing elements.
597       */       */
598        @SuppressWarnings("unchecked")
599      private E removeAt(int i) {      private E removeAt(int i) {
600          assert i >= 0 && i < size;          // assert i >= 0 && i < size;
601          modCount++;          modCount++;
602          int s = --size;          int s = --size;
603          if (s == i) // removed last element          if (s == i) // removed last element
# Line 556  Line 634 
634              siftUpComparable(k, x);              siftUpComparable(k, x);
635      }      }
636    
637        @SuppressWarnings("unchecked")
638      private void siftUpComparable(int k, E x) {      private void siftUpComparable(int k, E x) {
639          Comparable<? super E> key = (Comparable<? super E>) x;          Comparable<? super E> key = (Comparable<? super E>) x;
640          while (k > 0) {          while (k > 0) {
# Line 569  Line 648 
648          queue[k] = key;          queue[k] = key;
649      }      }
650    
651        @SuppressWarnings("unchecked")
652      private void siftUpUsingComparator(int k, E x) {      private void siftUpUsingComparator(int k, E x) {
653          while (k > 0) {          while (k > 0) {
654              int parent = (k - 1) >>> 1;              int parent = (k - 1) >>> 1;
# Line 596  Line 676 
676              siftDownComparable(k, x);              siftDownComparable(k, x);
677      }      }
678    
679        @SuppressWarnings("unchecked")
680      private void siftDownComparable(int k, E x) {      private void siftDownComparable(int k, E x) {
681          Comparable<? super E> key = (Comparable<? super E>)x;          Comparable<? super E> key = (Comparable<? super E>)x;
682          int half = size >>> 1;        // loop while a non-leaf          int half = size >>> 1;        // loop while a non-leaf
# Line 614  Line 695 
695          queue[k] = key;          queue[k] = key;
696      }      }
697    
698        @SuppressWarnings("unchecked")
699      private void siftDownUsingComparator(int k, E x) {      private void siftDownUsingComparator(int k, E x) {
700          int half = size >>> 1;          int half = size >>> 1;
701          while (k < half) {          while (k < half) {
# Line 635  Line 717 
717       * Establishes the heap invariant (described above) in the entire tree,       * Establishes the heap invariant (described above) in the entire tree,
718       * assuming nothing about the order of the elements prior to the call.       * assuming nothing about the order of the elements prior to the call.
719       */       */
720        @SuppressWarnings("unchecked")
721      private void heapify() {      private void heapify() {
722          for (int i = (size >>> 1) - 1; i >= 0; i--)          for (int i = (size >>> 1) - 1; i >= 0; i--)
723              siftDown(i, (E)queue[i]);              siftDown(i, (E)queue[i]);
# Line 642  Line 725 
725    
726      /**      /**
727       * Returns the comparator used to order the elements in this       * Returns the comparator used to order the elements in this
728       * queue, or <tt>null</tt> if this queue is sorted according to       * queue, or {@code null} if this queue is sorted according to
729       * the {@linkplain Comparable natural ordering} of its elements.       * the {@linkplain Comparable natural ordering} of its elements.
730       *       *
731       * @return the comparator used to order this queue, or       * @return the comparator used to order this queue, or
732       *         <tt>null</tt> if this queue is sorted according to the       *         {@code null} if this queue is sorted according to the
733       *         natural ordering of its elements.       *         natural ordering of its elements
734       */       */
735      public Comparator<? super E> comparator() {      public Comparator<? super E> comparator() {
736          return comparator;          return comparator;
737      }      }
738    
739      /**      /**
740       * Save the state of the instance to a stream (that       * Saves this queue to a stream (that is, serializes it).
      * is, serialize it).  
741       *       *
742       * @serialData The length of the array backing the instance is       * @serialData The length of the array backing the instance is
743       * emitted (int), followed by all of its elements (each an       *             emitted (int), followed by all of its elements
744       * <tt>Object</tt>) in the proper order.       *             (each an {@code Object}) in the proper order.
745       * @param s the stream       * @param s the stream
746         * @throws java.io.IOException if an I/O error occurs
747       */       */
748      private void writeObject(java.io.ObjectOutputStream s)      private void writeObject(java.io.ObjectOutputStream s)
749          throws java.io.IOException{          throws java.io.IOException{
750          // Write out element count, and any hidden stuff          // Write out element count, and any hidden stuff
751          s.defaultWriteObject();          s.defaultWriteObject();
752    
753          // Write out array length          // Write out array length, for compatibility with 1.5 version
754          // For compatibility with 1.5 version, must be at least 2.          s.writeInt(Math.max(2, size + 1));
         s.writeInt(Math.max(2, queue.length));  
755    
756          // Write out all elements in the proper order.          // Write out all elements in the "proper order".
757          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
758              s.writeObject(queue[i]);              s.writeObject(queue[i]);
759      }      }
760    
761      /**      /**
762       * Reconstitute the <tt>PriorityQueue</tt> instance from a stream       * Reconstitutes the {@code PriorityQueue} instance from a stream
763       * (that is, deserialize it).       * (that is, deserializes it).
764         *
765       * @param s the stream       * @param s the stream
766         * @throws ClassNotFoundException if the class of a serialized object
767         *         could not be found
768         * @throws java.io.IOException if an I/O error occurs
769       */       */
770      private void readObject(java.io.ObjectInputStream s)      private void readObject(java.io.ObjectInputStream s)
771          throws java.io.IOException, ClassNotFoundException {          throws java.io.IOException, ClassNotFoundException {
772          // Read in size, and any hidden stuff          // Read in size, and any hidden stuff
773          s.defaultReadObject();          s.defaultReadObject();
774    
775          // Read in array length and allocate array          // Read in (and discard) array length
776          int arrayLength = s.readInt();          s.readInt();
777          queue = new Object[arrayLength];  
778            queue = new Object[size];
779    
780          // Read in all elements in the proper order.          // Read in all elements.
781          for (int i=0; i<size; i++)          for (int i=0; i<size; i++)
782              queue[i] = (E) s.readObject();              queue[i] = s.readObject();
783    
784            // Elements are guaranteed to be in "proper order", but the
785            // spec has never explained what that might be.
786            heapify();
787        }
788    
789        public Spliterator<E> spliterator() {
790            return new PriorityQueueSpliterator<E>(this, 0, -1, 0);
791        }
792    
793        /**
794         * This is very similar to ArrayList Spliterator, except for extra
795         * null checks.
796         */
797        static final class PriorityQueueSpliterator<E> implements Spliterator<E> {
798            private final PriorityQueue<E> pq;
799            private int index;            // current index, modified on advance/split
800            private int fence;            // -1 until first use
801            private int expectedModCount; // initialized when fence set
802    
803            /** Creates new spliterator covering the given range */
804            PriorityQueueSpliterator(PriorityQueue<E> pq, int origin, int fence,
805                                 int expectedModCount) {
806                this.pq = pq;
807                this.index = origin;
808                this.fence = fence;
809                this.expectedModCount = expectedModCount;
810            }
811    
812            private int getFence() { // initialize fence to size on first use
813                int hi;
814                if ((hi = fence) < 0) {
815                    expectedModCount = pq.modCount;
816                    hi = fence = pq.size;
817                }
818                return hi;
819            }
820    
821            public Spliterator<E> trySplit() {
822                int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
823                return (lo >= mid) ? null :
824                    new PriorityQueueSpliterator<E>(pq, lo, index = mid,
825                                                    expectedModCount);
826            }
827    
828            @SuppressWarnings("unchecked")
829            public void forEachRemaining(Consumer<? super E> action) {
830                int i, hi, mc; // hoist accesses and checks from loop
831                PriorityQueue<E> q; Object[] a;
832                if (action == null)
833                    throw new NullPointerException();
834                if ((q = pq) != null && (a = q.queue) != null) {
835                    if ((hi = fence) < 0) {
836                        mc = q.modCount;
837                        hi = q.size;
838                    }
839                    else
840                        mc = expectedModCount;
841                    if ((i = index) >= 0 && (index = hi) <= a.length) {
842                        for (E e;; ++i) {
843                            if (i < hi) {
844                                if ((e = (E) a[i]) == null) // must be CME
845                                    break;
846                                action.accept(e);
847                            }
848                            else if (q.modCount != mc)
849                                break;
850                            else
851                                return;
852                        }
853                    }
854                }
855                throw new ConcurrentModificationException();
856            }
857    
858            public boolean tryAdvance(Consumer<? super E> action) {
859                int hi = getFence(), lo = index;
860                if (lo >= 0 && lo < hi) {
861                    index = lo + 1;
862                    @SuppressWarnings("unchecked") E e = (E)pq.queue[lo];
863                    if (e == null)
864                        throw new ConcurrentModificationException();
865                    action.accept(e);
866                    if (pq.modCount != expectedModCount)
867                        throw new ConcurrentModificationException();
868                    return true;
869                }
870                return false;
871            }
872    
873            public long estimateSize() {
874                return (long) (getFence() - index);
875      }      }
876    
877            public int characteristics() {
878                return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;
879            }
880        }
881  }  }

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